Skin Infections, Infestations and Drug Eruptions Flashcards
What is scabies
High contagious infestation by the mite Sarcoptes Sacbiei. Spread is via direct contact.
What is the pathophysiology of scabies
Female mite digs a burrow that looks like a short wavy, grey or red lines on the skin surface
Here she lays eggs which hatch as larvae. The itch and red rash that follows occurs due to allergic sensitivity to the larvae 30 days later delayed type IV hypersensitivity reaction.
How does scabies present?
Papules, vesicles, pustules and nodules affecting finger webs, wrist, flexures, axillae, abdomen (especially waistband and umbilicus), buttocks and groins
Secondary features such as excoriation and infection occur due to scratching
Who needs to be treated after a scabies infection?
Treat all members of the household and all close contacts even if asymptomatic and avoid physical contact with others until treatment complete
What are the management options for scabies?
First line – Permethrin 5% dermal cream – safe in pregnancy
Second line – Malathion 0.5% is second line – not safe in pregnancy
Oral ivermectin if severe such as crusted (Norwegian) scabies
Rash and itch take 4-6 weeks to settle – anti-pruritic cream crotamiton can be useful in this time
What advice should you give regarding the applying of creams/ointments for scabies?
Take a warm bath with soap all over the skin
Scrub finger nails with a firm brush
Apply cream given for treatment all over body (contrary to manufacturers advice) paying particular attention to between skin folds e.g. fingers and toes and wash after 8-10 hours for permethrin or 24 hours for malathion
Wash all towels, sheets etc.
Reapply if removed during the day e.g. hand washing or nappy change.
Repeat treatment after 7 days
Treatment may worsen itch in first 2 weeks
What is the difference between nits and lice?
Lice are the insect; nits are the eggs. Also known as Pediculosis capitis.
How do nits/lice present?
Usually asymptomatic, presents due to lice being seen
Itch and rash on nape of neck
Head lice are spread by direct head-to-head contact and therefore tend to be more common in children because they play closely together. They cannot jump, fly or swim! When newly infected, cases have no symptoms but itching and scratching on the scalp occurs 2 to 3 weeks after infection. There is no incubation period.
How are headlice managed?
2 applications 7 days apart of Malathion, then shampoo and rinse + fine toothed combing
Dimectome and Isopropyl myristate and cyclomethicone are alternative (last two not suitable in under 2s or with skin conditions)
School exclusion not required nor treatment of household contacts
Treat crab lice – sexually transmitted in the same way
What is a dermatophyte infection?
This is also known as ringworm or tinea followed by the part of the body it affects e.g. tinea pedis (athlete’s foot), cruris (groin), capitis, unguium (nail) and corporis (body). It is a fungal infection that invade and grow in dead keratin. Spread is indirectly via person to person.
What causes dermatophyte infections?
The most common cause is usually human only e.g. Trichophyton rubrum.
Species that also infect animals tend to induce more inflammation such as Microsporum gypseum.
How does ringworm present?
Round, scaly, itchy, lesion
Edge more inflamed than the centre
In children can cause a scarring alopecia
If left untreated will form into a Kerion
How should ring worm be investigated?
Send samples e.g. scalp scraping for microscopy
How is ring worm managed?
Generally oral antifungal e.g. terbinafine, imidazole or fluconazole twice daily for 2 weeks – 4 weeks
Where does candida most commonly infect?
Most commonly infects, skin folds, mouth, vagina, glans penis, toe web and nail areas.
What is candida intertrigo and how does it present?
Candida Intertrigo (skin folds) Appears as erythematous and macerated plaques with peripheral scaling associated with moist pink satellite papules or pustules. In hot damp skin folds such as under the breast or under abdominal fat folds, arm pits and groin and webbed spaces between fingers and toes.
How does oral candida present?
White patches seen on the gums, tongue and inside the mouth, they can be peeled off leaving a raw area.
How is candida treated in different locations?
Skin – clotrimazole cream or if severe oral such as fluconazole
Mouth – oral nystatin or miconazole gel. Can also get antifungal mouthwashes e.g. Triclosan
Vagina – imidazole cream and/or pessary
What is pityriasis versicolor?
Also known as tinea versicolor is a superficial cutaneous fungal infection caused be Malassezia which results in multiple hypopigmented, white or brown scaly macules on the upper trunk and back. They produce an acid that prevents tanning and can be itchy.
What are the risk factors for pityriasis versicolor?
Usually healthy individuals
Immunosuppression
Malnutrition
Cushing’s
How is pityriasis versicolor managed?
Treat with ketoconazole shampoo as is most effective for large areas.
If failure to respond, consider alternate diagnosis and give oral itraconazole.
What is impetigo?
Contagious superficial infection caused to staph aureus and sometimes strep pyogenes. Usually seen in kids 2-5yrs either as a primary infection or a complication of an existing skin condition.
How does impetigo present?
Lesions are well defined and start on the nose and face with a honey coloured crust on an erythematous base.
How is impetigo managed?
If limited and localised then hydrogen peroxide 1% cream first line,
2nd line topical fusidic acid or mupirocin if MRSA and resistant to fusidic acid
If extensive then oral flucloxacillin, or oral erythromycin
Exclusion from school until lesions crusted and healed or 48 hours after commencing antibiotic treatment
Should children with impetigo be excluded from school?
Extremely contagious – kids should be excluded from school until lesions are crusted and healed or 48 hours after commencing antibiotic treatment.
What is cellulitis?
Acute infection of skin and soft tissues. Erysipelas is a superficial form but they are usually considered the same infection.
What typically causes cellulitis?
Typically, Streptococcus pyogenes (beta strep) or staphylococcus aureus
How does cellulitis present?
Unilateral symptoms Pain Swelling Erythema Warmth Systemic upset Lymphadenopathy Can be a complication of existing condition e.g. eczema Can occur on flexures of limbs as well as face
How is cellulitis severity classified?
Eron Classification for management of Cellulitis
Describe the 4 types of cellulitis according to Eron classification?
I There are no signs of systemic toxicity and the person has no uncontrolled co-morbidities
II The person is either systemically unwell or systemically well but with a co-morbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection
III The person has significant systemic upset such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable co-morbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize
IV The person has sepsis syndrome or a severe life-threatening infection such as necrotizing fasciitis
When should someone with cellulitis be admitted?
Class III or IV cellulitis Under the age of 1 or frail Immunocompromised Significant lymphoedema Facial cellulitis
How is cellulitis managed?
Elevate affected part
Oral Flucloxacillin
Clarithromycin, erythromycin (in pregnancy) or doxycycline in penicillin allergic
If penicillin allergic try erythromycin or doxycycline
If severe – co-amoxiclav, cefuroxime, clindamycin or ceftriaxone
What is necrotising fasciitis?
Rapidly deteriorating infection of the deep fascia that results in necrosis of the subcutaneous tissue due to thrombus formation that causes ischaemia.
What are the 3 types of necrotising fasciitis?
Type 1 (most common) – mixed anaerobes and aerobes (often post-surgery in diabetics). Often involves staphylococcus aureus, haemophilus, and others.
Type 2 – streptococcus pyogenes
Type 3 – gas gangrene from clostridium perfringens
How does necrotising fasciitis present?
Acute onset
Painful erythematous lesions
Purple rash and large dark marks that turn into blisters with dark fluid
Oedema
Rapidly worsening cellulitis with pain out of keeping with physical features
Extremely tender over infected tissues
How should necrotising fasciitis be managed?
Urgent Surgical referral for debridement
IV antibiotics such as benzylpenicillin or clindamycin
Describe the appearance of a common viral wart
Papules or nodules with a hyperkeratotic surface
Seen at sites of trauma – fingers, elbows, knees, pressure points on soles
May coalesce into confluent lesions (mosaic warts)
Rarely cause symptoms and disappear spontaneously within months to years
What causes the common viral wart e.g. verruca?
Usually as a result of a human papillomavirus
What management is given and when should it be offered for the viral wart?
Only if painful, unsightly, or persisting
Topical salicylic acid (first soften in warm water, then rub with rough surface, cover in gel then allow to dry then cover in plaster or tape)
Cryotherapy – once every 3-4 weeks for 4 cycles
Duct tape occlusion – 6 days at a time for 8 weeks
Genital warts – self applied podophyllin or imiquimod
What is molluscum contagiosum?
Skin infection caused by the molluscum contagiosum virus. Transmission by close contact or contaminated surfaces.
How does molluscum contagiosum present?
Pink or pearly white papules with an umbilicated central punctum. Appear in clusters anywhere on the body except the palms of hands and soles of feet. Common in children especially ages 1-4.
How is mollusucum contagiosum managed?
Usually resolve spontaneously after a few months.
Treatment not required
Gentle cryotherapy or squeezing/piercing may be tried.
What is a morbilliform rash?
Most common reaction to drugs presenting with a generalised macula-papula rash and a fever within 1-3 weeks of drug exposure. Not mucosal involvement.
Which drugs commonly cause a morbilliform rash?
Common culprits: amoxicillin, cephalosporins, anti-epileptics, sulphonamides, allopurinol, captopril, and thiazides.
What is urticaria?
Itchy, erythematous wheals that move around and appear rapidly after drug administration. Can include angioedema and anaphylaxis. IgE mediated.
What drugs commonly cause urticaria?
Common culprits: penicillins, cephalosporins, opiate, NSAIDs, ACEi, thiazides and phenytoin.
What is steven Johnson syndrome?
Vague upper respiratory tract symptoms 2-3 weeks after starting a drug and 2 days before a rash covering <10% of the body. Painful erythematous macules evolving to target lesions. Severe mucosal ulceration of multiple surfaces.
What commonly causes steven johnson syndrome?
Common culprits: sulphonamides, antiepileptics, penicillins and NSAIDs
What is toxic epidermal necrolysis?
Flu like symptoms preceding skin involvement affecting >30% of body. Wide spread painful dusky erythema, leading to necrosis of large sheets of epidermis. Mucosae severely affected and mortality is 30%.
What drugs commonly causes toxic epidermal necrolysis?
Common Culprits: sulphonamides, anti-epileptics, penicillins, cephalosporins, allopurinol and NSAIDs.
How is steven johnson syndrome and toxic epidermal necrolysis managed?
Supportive in ICU, HDU or burns unit with fluids and analgesia
IV Ig commonly used first line
Avoid steroids and protect skin but do not debride
What is staphylococcal scalded skin syndrome?
Red blistering skin that looks like a burn or a scald. Caused by exotoxins A and B released from certain strains of staphylococcus aureus. It usually occurs in children under the age of 5yrs, particularly neonates because their immature renal system cannot filter out the toxins. It is unlikely to occur in adults due to lifelong immunity often gained in childhood.
How is staphylococcal scalded skin syndrome managed?
Hospitalisation
IV antibiotics – flucloxacillin
DO NOT given steroids
Analgesia
What are the CDC diagnostic criteria for toxic shock syndrome?
Fever >38.9 Hypotension – Systolic < 90 Diffuse erythematous rash Desquamation of rash on palms and soles Involvement of 3 or more systems e.g. GI – N+V and diarrhoea, renal failure, mucous membrane erythema, hepatitis, thrombocytopenia, CNS involvement i.e. confusion.
How is toxic shock syndrome managed?
Remove source if infection
IV antibiotics e.g. flucloxacillin
Supportive care
What is pityriasis rosea?
Acute self-limiting (disappears after 6-12 weeks) rash in young adults probably as a result of Herpes hominis virus 7.
How does pityriasis rosea present?
Some give a history of recent viral infection most there is no prodrome. Herald rash on trunk followed by erythematous oval, scaly patches following a characteristic distribution with the longitudinal diameters of the oval lesions running parallel to the ling of langer causing a fir tree appearance.
